A process for the fabrication of semiconductor devices having various buried regions

摘要

The process provides for doping a P-type substrate (50) by forming a mask (52) of silicon nitride, implanting N-type impurities through this mask (Figure 7), forming a resist mask (54) which leaves at least one area of the substrate (Figure 8) containing a part of the nitride mask exposed, implanting N-type impurities first with an insufficient energy and then with a sufficient energy to traverse the nitride mask, subjecting (Figure 9) the substrate to a high temperature treatment in an oxidising environment to form silicon dioxide pads (55) on the areas of the substrate not covered by the nitride mask, removing the nitride mask and performing an implantation of P-type impurities into the areas delimited by the pads. The process then continues with the removal of the pads and, in the conventional manner, with the formation of an epitaxial layer and selective doping of this to form P-type and N-type regions in it. The process described allows the production of integrated devices with an additional buried layer whilst utilising one fewer mask than conventional processes. <IMAGE> <IMAGE> <IMAGE> <IMAGE>